Advance of computer technology has made keyboard a necessary fundamental input device. While many types of computer equipments have been developed the keyboard generally is maintained its fundamental style. However, in order to meet varying users' requirements the size and weight of the keyboard have been greatly reduced in recent years. Foldable and extendable keyboards, and even flexible keyboards that can be rolled and bent also have been developed and marketed. The critical issue that constrains the usability of the keyboard is signal line connection that links the keyboard and computer equipments. The length of the signal line becomes a constraint on use distance and location. To overcome this limitation, keyboards equipped with wireless communication technique have been developed by some producers, such as Bluetooth wireless keyboards, infrared wireless keyboard and the like.
Although the keyboard linked via wireless communication has resolved a lot of problems of the conventional keyboard, a lot of people these days often have many types of information processing systems on hand, such as computers, handsets and tablet computers. If each information processing system is equipped with a wireless keyboard mix-up could occur when in use. Hence some producers have developed a wireless keyboard capable of switching among multiple linking targets. The wireless keyboard can register the linking data of at least two information processing systems at the same time. Through the registered linking data users can freely switch linking between the two information processing systems. However, the present wireless keyboard for switching among multiple linking targets cannot display the current linked information processing system. Even if the wireless keyboard displays a currently chosen transmission channel selection code, the problem of blind switching could still occur. This is mainly caused by user's forgetting the originally setting transmission channel after a period of time that could result in user's switching randomly each transmission channel until a successful link is established. Hence even if the transmission channel selection code is displayed, user still has difficulty to remember the exact information processing system originally set, and the problem of blind switching could still happen.